Combined mechanical and electronic image stabilization

ABSTRACT

Systems and methods are disclosed for image signal processing. For example, methods may include determining a sequence of orientation estimates based on sensor data from one or more motion sensors; based on the sequence of orientation estimates, invoking a mechanical stabilization system to reject motions of an image sensor occurring within a first operating bandwidth with an upper cutoff frequency; receiving an image from the image sensor; based on the sequence of orientation estimates, invoking an electronic image stabilization module to correct the image for rotations of the image sensor occurring within a second operating bandwidth with a lower cutoff frequency to obtain a stabilized image, wherein the lower cutoff frequency is greater than the upper cutoff frequency; and storing, displaying, or transmitting an output image based on the stabilized image.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/563,224, filed Sep. 26, 2017, and U.S. Provisional Application No.62/614,140, filed Jan. 5, 2018, the contents of which are incorporatedby reference herein in their entirety.

TECHNICAL FIELD

This disclosure relates to image stabilization for image capture.

BACKGROUND

Image capture devices, such as cameras, may capture content as images orvideo. Light may be received and focused via a lens and may be convertedto an electronic image signal by an image sensor. The image signal maybe processed by an image signal processor (ISP) to form an image, whichmay be stored and/or encoded. In some implementations, multiple imagesor video frames from different image sensors may include spatiallyadjacent or overlapping content, which may be stitched together to forma larger image with a larger field of view.

SUMMARY

Disclosed herein are implementations of image stabilization for imagecapture.

In a first aspect, the subject matter described in this specificationcan be embodied in systems that include an image sensor configured tocapture an image; a mechanical stabilization system, including motors,configured to control an orientation of the image sensor to rejectmotions occurring within a first operating bandwidth with an uppercutoff frequency; and an electronic image stabilization moduleconfigured to correct images for rotations of the image sensor occurringwithin a second operating bandwidth with a lower cutoff frequency toobtain a stabilized image, wherein the lower cutoff frequency is greaterthan the upper cutoff frequency.

In a second aspect, the subject matter described in this specificationcan be embodied in methods that include determining a sequence oforientation estimates based on sensor data from one or more motionsensors; based on the sequence of orientation estimates, invoking amechanical stabilization system to reject motions of an image sensoroccurring within a first operating bandwidth with an upper cutofffrequency; receiving an image from the image sensor; based on thesequence of orientation estimates, invoking an electronic imagestabilization module to correct the image for rotations of the imagesensor occurring within a second operating bandwidth with a lower cutofffrequency to obtain a stabilized image, wherein the lower cutofffrequency is greater than the upper cutoff frequency; and storing,displaying, or transmitting an output image based on the stabilizedimage.

In a third aspect, the subject matter described in this specificationcan be embodied in systems that include an image sensor configured tocapture an image; one or more motion sensors configured to detect motionof the image sensor; a mechanical stabilization system, includinggimbals and motors, configured to control an orientation of the imagesensor; and an electronic image stabilization module configured tocorrect images for rotations of the image sensor. The systems include aprocessing apparatus configured to determine a sequence of orientationestimates based on sensor data from the one or more motion sensors;based on the sequence of orientation estimates, invoke the mechanicalstabilization system to reject motions occurring within a firstoperating bandwidth with an upper cutoff frequency; receive the imagefrom the image sensor; based on the sequence of orientation estimates,invoke the electronic image stabilization module to correct the imagefor rotations of the image sensor occurring within a second operatingbandwidth with a lower cutoff frequency to obtain a stabilized image,wherein the lower cutoff frequency is greater than the upper cutofffrequency; and store, display, or transmit an output image based on thestabilized image.

These and other aspects of the present disclosure are disclosed in thefollowing detailed description, the appended claims, and theaccompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure is best understood from the following detaileddescription when read in conjunction with the accompanying drawings. Itis emphasized that, according to common practice, the various featuresof the drawings are not to-scale. On the contrary, the dimensions of thevarious features are arbitrarily expanded or reduced for clarity.

FIG. 1 is a block diagram of a movable imaging system and high-levelcomponents.

FIG. 2A is a pictorial illustration of a movable imaging assembly.

FIG. 2B is a pictorial illustration of the imaging device.

FIG. 2C is a pictorial illustration of a movable imaging assemblycontroller and user interface.

FIG. 2D is a pictorial illustration of the imaging device of FIG. 2Bwithin a movement mechanism.

FIG. 3A is a block diagram of an example of a system configured forimage capture with image stabilization.

FIG. 3B is a block diagram of an example of a system configured forimage capture with image stabilization.

FIG. 4 is a block diagram of an example of a system configured for imagecapture with image stabilization.

FIG. 5 is a flowchart of an example of a process for image capture withmechanical and electronic image stabilization.

FIG. 6 is a flowchart of an example of a process for adjusting theoperating bandwidths of a mechanical stabilization system and anelectronic image stabilization module.

FIG. 7 is a plot of an example of a transfer function of an MSS filter,corresponding to the operating bandwidth of the MSS, overlaid with atransfer function of an EIS filter, corresponding to the operatingbandwidth of the EIS.

FIG. 8A is a pictorial illustration of an example of an image capturemodule from a first perspective.

FIG. 8B is a pictorial illustration of an example of an image capturemodule from a second perspective.

FIG. 9A is a pictorial illustration of an example of a handheld modulefrom a first perspective.

FIG. 9B is a pictorial illustration of an example of a handheld modulefrom a second perspective.

FIG. 10A is a pictorial illustration of an example of a handheld moduleoriented to be connected to an image capture module.

FIG. 10B is a pictorial illustration of an example of a movable imagingassembly in communication with a personal computing device.

DETAILED DESCRIPTION

This document includes disclosure of systems, apparatus, and methods forimage capture with combined mechanical and electronic imagestabilization. Electronic image stabilization (EIS) and mechanicalstabilization systems (MSS) attempt to solve the same problem usingsimilar data. Typical implementations do not operate properly at thesame time. Typical electronic image stabilization modules may usegyroscope data to correct for camera rotational motion around the X, Y,and, Z axis of the camera frame. Typical mechanical stabilizationsystems may use gyroscope and/or accelerometer data as well asoptionally magnetometer, barometer, and global positioning system datato reject roll motion in X, Y, and Z axis of a gimbal frame as well astranslational motion in X, Y, And Z axis in the gimbal frame. Amechanical stabilization system may be configured to reject motion whileelectronic image stabilization module corrects motion artifacts in acaptured image (e.g., a frame of video). A mechanical stabilizationsystem works in the gimbal frame of reference (which may be differentfor each axis) while an electronic image stabilization module works onthe camera frame of reference.

A mechanical stabilization system may reject motion within someoperating bandwidth, which may extend from a lower cutoff frequency,MSS_L_CF, to an upper cutoff frequency, MSS_U_CF. An electronic imagestabilization module will reject motion within some operating bandwidth,which may extend from a lower cutoff frequency, EIS_L_CF, to an uppercutoff frequency, EIS_U_CF.

Using both a mechanical stabilization system and an electronic imagestabilization module simultaneously in the same image capture system maylead to interference between the dynamics of the two systems, which mayactually degrade image (e.g., video quality). Another problem is that amechanical stabilization system may require high power consumption anddrain a battery of an image capture system. Another problem is that anelectronic image stabilization module may be computationally complex andconsume significant computing resources (e.g., processor cycles ormemory). Another problem is that a mechanical stabilization systemtypically has motors that can overheat when too much power is consumed.

A technique is proposed where the operation of both a mechanicalstabilization system and an electronic image stabilization module isaltered by altering the control response of each system. Adaptivecontrollers can throttle the bandwidth. To improve power usage themechanical stabilization system, its operating bandwidth can be limitedsuch that it does not overlap with the operating bandwidth of theelectronic image stabilization module. To conserve computing resources,the operating bandwidth of the electronic image stabilization module canbe limited such that it does not overlap with the operating bandwidth ofthe mechanical stabilization system. An image capture system maydynamically adapt the allocation of operating bandwidth betweenmechanical stabilization system and the electronic image stabilizationmodule to improve system performance (e.g., to improve thermalperformance and/or battery life performance). For example, operatingbandwidths can be adjusted in a complimentary manner to limit theoperating bandwidth of the mechanical stabilization system when motorsstart to heat up and compensate by increasing the operating bandwidth ofthe electronic image stabilization module to cover the operatingbandwidth gap. Adjustment of the operating bandwidth allocation betweenthe between mechanical stabilization system and the electronic imagestabilization module can be a user selectable feature or adjustedautomatically.

Implementations are described in detail with reference to the drawings,which are provided as examples so as to enable those skilled in the artto practice the technology. The figures and examples are not meant tolimit the scope of the present disclosure to a single implementation orembodiment, and other implementations and embodiments are possible byway of interchange of, or combination with, some or all of the describedor illustrated elements. Wherever convenient, the same reference numberswill be used throughout the drawings to refer to same or like parts.

FIG. 1 is a block diagram of a movable imaging system 10 and high-levelcomponents. The movable imaging system 10 may have two primarycomponents: a movable imaging assembly 20 (MIA) and an external device50, such as an MIA controller with a user interface. These componentsmay be communicatively connected via a link 55. The link 55 may bewireless or wired. Other components may also be included within themovable imaging system 10. For example, the movable imaging assembly 20may comprise an imaging device 100, such as a camera (as used herein,the term “camera” is defined broadly to include any form of imagingdevice) that can be used to capture still and video images. The movableimaging assembly 20 may include a movable platform 40 that can be movedpositionally and/or rotationally with respect to a fixed referenceground. The movable imaging assembly 20 may also include a movementmechanism 30 that allows the imaging device 100 to move positionallyand/or rotationally with respect to the movable platform 40.

In some implementations, the external device 50 may correspond to asmartphone, a tablet computer, a phablet, a smart watch, a portablecomputer, and/or another device configured to receive user input andcommunicate information with the imaging device 100, movement mechanism30, and/or movable platform 40 individually, or with the movable imagingassembly 20 as a whole.

In one or more implementations, the link 55 may utilize any wirelessinterface configuration, e.g., WiFi, Bluetooth (BT), cellular data link,ZigBee, near field communications (NFC) link, e.g., using ISO/IEC 14443protocol, ANT+ link, and/or other wireless communications link. In someimplementations, the link 55 may be effectuated using a wired interface,e.g., HDMI, USB, digital video interface, display port interface (e.g.,digital display interface developed by the Video Electronics StandardsAssociation (VESA), Ethernet, Thunderbolt), and/or other interface.

The UI of the external device 50 may operate a software application(e.g., GoPro Studio®, GoPro App®, and/or other application) configuredto perform a variety of operations related to camera configuration,control of video acquisition, and/or display of video captured by theimaging device 100. An application (e.g., GoPro App)® may enable a userto create short video clips and share video clips to a cloud service(e.g., Instagram®, Facebook®, YouTube®, Dropbox®); perform full remotecontrol of imaging device 100 functions; live preview video beingcaptured for shot framing; mark key moments while recording (e.g.,HiLight Tag®, View HiLight Tags in GoPro Camera Roll®) for locationand/or playback of video highlights; wirelessly control camera software;and/or perform other functions. Various methodologies may be utilizedfor configuring the imaging device 100 and/or displaying the capturedinformation.

By way of an illustration, the UI of the external device 50 may receivea user setting characterizing image resolution (e.g., 3840 pixels by2160 pixels), frame rate (e.g., 60 frames per second (fps)), and/orother settings (e.g., location) related to an activity (e.g., mountainbiking) being captured by the user. The UI of the external device 50 maycommunicate these settings to the imaging device 100 via the link 55.

A user may utilize the UI of the external device 50 to view contentacquired by the imaging device 100. A display of the UI of the externaldevice 50 may act as a viewport into a 3D space of the content. In someimplementations, the UI of the external device 50 may communicateadditional information (e.g., metadata) to the imaging device 100. Byway of an illustration, the UI of the external device 50 may provideorientation of the UI of the external device 50 with respect to a givencoordinate system to the imaging device 100 to enable determination of aviewport location or dimensions for viewing of a portion of thepanoramic content, or both. By way of an illustration, a user may rotate(sweep) the UI of the external device 50 through an arc in space. The UIof the external device 50 may communicate display orientationinformation to the imaging device 100 using a communication interfacesuch as link 55. The imaging device 100 may provide an encoded bitstreamconfigured to enable viewing of a portion of the content correspondingto a portion of the environment of the display location as the imagingdevice 100 traverses the path. Accordingly, display orientationinformation sent from the UI of the external device 50 to the imagingdevice 100 allows user selectable viewing of captured image and/orvideo.

In many instances, it is desirable to track a target (which may includeone or more subjects) with the movable imaging assembly 20. Variousforms of tracking may be utilized, including those discussed below andin U.S. Provisional Patent Application Ser. No. 62/364,960, filed Jul.21, 2016, and herein incorporated by reference in its entirety. Atracking system 60 may be utilized to implement the described forms oftracking. The tracking system 60 may comprise a processor and algorithmsthat are used for tracking the target. The tracking system 60 is shownin dashed lines since it may be included entirely within the movableimaging assembly 20 or entirely within the external device 50, orportions of the tracking system 60 may be located or duplicated withineach of the movable imaging assembly 20 and the external device 50. Avoice recognition system 70 may also be utilized to interact with thetracking system 60 and issue commands (e.g., commands identifying oradjusting a target).

FIGS. 2A-2D are pictorial illustrations of implementations of thecomponents shown in FIG. 1.

FIG. 2A is a pictorial illustration of the movable imaging assembly 20.In the example implementation shown, the movable imaging assembly 20includes a movable platform 40 that is a quadcopter drone. The movableimaging assembly 20 could be any form of an aerial vehicle or any formof movable device that is movable with respect to a fixed ground, whichcould include movable mechanical systems that are tied to the earth. Asshown in FIG. 2A, the imaging device 100 is mounted in the front of themovable platform 40 so that it points in a direction along an axis ofthe movable platform 40. However, in various implementations, themounting of the imaging device 100 to the movable platform 40 is doneusing the movement mechanism 30.

FIG. 2B is a pictorial illustration of the imaging device 100. In FIG.2B, the imaging device 100 is a GoPro Hero4® camera, however any type ofimaging device 100 may be utilized. The imaging device 100 may include avideo camera device. FIG. 2B also shows a lens 130 of the camera, alongwith a display screen 147.

FIG. 2C is a pictorial illustration of an external device 50,specifically, an MIA controller and user interface. The user interfacemay further comprise a display system 51 with a display device 52. TheMIA controller may further comprise a communications interface via whichit may receive commands both for operation of the movable platform 40,such as the UAV or drone, and operation of the imaging device 100. Thecommands can include movement commands, configuration commands, andother types of operational control commands.

FIG. 2D is a pictorial illustration of the imaging device 100 of FIG. 2Bwithin the movement mechanism 30. The movement mechanism 30 couples theimaging device 100 to the movable platform 40. The implementation of themovement mechanism 30 shown in FIG. 2D is a three-axis gimbal mechanismthat permits the imaging device 100 to be rotated about threeindependent axes. However, the movement mechanism 30 may include anytype of translational and/or rotational elements that permit rotationaland/or translational movement in one, two, or three dimensions.

FIG. 3A is a block diagram of an example of a system 300 configured forimage capture with image stabilization. The system 300 includes an imagecapture device 310 (e.g., a camera or a drone) that includes aprocessing apparatus 312 that is configured to receive images from oneor more image sensors 314. The image capture device 310 includes gimbalsand motors 316 that are actuators of a mechanical stabilization systemconfigured to control an orientation of the one or more image sensors314 (e.g., an orientation with respect to a movable platform). Thegimbals and motors 316 may be controlled by a controller of themechanical stabilization system, which may be implemented by theprocessing apparatus 312 (e.g., as a software module or a specializedhardware module). The processing apparatus 312 may be configured toperform image signal processing (e.g., filtering, tone mapping,stitching, and/or encoding) to generate output images based on imagedata from the image sensor 314. The processing apparatus 312 may includean electronic image stabilization module (e.g., implemented as asoftware module or a specialized hardware module) configured to correctimages for rotations of the one or more image sensors 314. The imagecapture device 310 includes one or more motion sensors 318 configured todetect motion of the one or more image sensors 314. The one or moremotion sensors 318 may provide feedback signals to the mechanicalstabilization system and/or electronic image stabilization module. Theimage capture device 310 includes a communications interface 322 fortransferring images to other devices. The image capture device 310includes a user interface 320, which may allow a user to control imagecapture functions and/or view images. The image capture device 310includes a battery 324 for powering the image capture device 310. Forexample, the system 300 may be used to implement processes described inthis disclosure, such as the process 500 of FIG. 5 and the process 600of FIG. 6.

The processing apparatus 312 may include one or more processors havingsingle or multiple processing cores. The processing apparatus 312 mayinclude memory, such as random access memory device (RAM), flash memory,or any other suitable type of storage device such as a non-transitorycomputer readable memory. The memory of the processing apparatus 312 mayinclude executable instructions and data that can be accessed by one ormore processors of the processing apparatus 312. For example, theprocessing apparatus 312 may include one or more DRAM modules such asdouble data rate synchronous dynamic random-access memory (DDR SDRAM).In some implementations, the processing apparatus 312 may include adigital signal processor (DSP). In some implementations, the processingapparatus 312 may include an application specific integrated circuit(ASIC). For example, the processing apparatus 312 may include a customimage signal processor. In some implementations, the processingapparatus 312 may have multiple processing units in different portionsthe image capture device 310. For example, the processing apparatus 312may include a processor on a movable platform (e.g., the movableplatform 40) and a processor in an imaging device (e.g., the imagingdevice 100) that are connected by the gimbals and motors 316.

The processing apparatus 312 may include an electronic imagestabilization module configured to correct images for rotations of animage sensor. For example, the electronic image stabilization module mayimplemented by software executed by the processing apparatus 312. Theelectronic image stabilization module may take sensor data (e.g.,gyroscope data) and/or orientation estimates for the image sensor asinput, determine a corrective rotation, and apply the correctiverotation to an image from the image sensor to obtain a stabilized image.

The one or more image sensors 314 are configured to capture images. Theone or more image sensors 314 are configured to detect light of acertain spectrum (e.g., the visible spectrum or the infrared spectrum)and convey information constituting an image as electrical signals(e.g., analog or digital signals). For example, the one or more imagesensors 314 may include charge-coupled devices (CCD) or active pixelsensors in complementary metal-oxide-semiconductor (CMOS). The one ormore image sensors 314 may detect light incident through respective lens(e.g., a fisheye lens). In some implementations, the one or more imagesensors 314 include digital to analog converters. In someimplementations, the one or more image sensors 314 have respectivefields of view that overlap.

The mechanical stabilization system for the one or more image sensors314 includes the gimbals and motors 316. The gimbals and motors 316 maybe parts of a movement mechanism (e.g., the movement mechanism 30). Thegimbals and motors 316 may connect the one or more image sensors 314 toa moving platform and control their orientation. For example, the imagecapture device 310 may include a drone that is coupled to a housing ofthe image sensor(s) 314 by the gimbals of the mechanical stabilizationsystem. The gimbals and motors 316 may span multiple axes (e.g., a3-axis gimbal set with brushless direct current motors). The mechanicalstabilization system may include a controller (e.g., a proportionalintegral derivative (PID) controller). For example, the controller ofthe mechanical stabilization system may be implemented by the processingapparatus 312 (e.g., as a software module or a specialized hardwaremodule).

The one or more motion sensors 318 are configured to detect motion ofthe one or more image sensors 314. For example, the one or more motionsensors 318 may include parts of an inertial measurement unit (e.g.,including gyroscopes, accelerometers, and/or magnetometers) that ismounted in a housing with the one or more image sensors 314. In someimplementations, the one or more motion sensors 318 may include parts ofan inertial measurement unit that is mounted in a movable platform ofthe image capture device 310. In some implementations, the one or moremotion sensors 318 includes sensors (e.g., magnetic encoders, opticalencoders, and/or potentiometers) that detect the state of the gimbalsand motors 316 to measure a relative orientation of the image sensor anda movable platform of the image capture device 310. The processingapparatus 312 may be configured to determine a sequence of orientationestimates based on sensor data from the one or more motion sensors 318.For example, determining the sequence of orientation estimates mayinclude applying quadratic estimation to sensor data from a plurality ofthe one or more motion sensors 318.

The processing apparatus 312 may be configured to invoke the mechanicalstabilization system and the electronic image stabilization module incombination to mitigate distortion of captured images due to motion ofthe image capture device 310. The processing apparatus 312 may beconfigured to, based on the sequence of orientation estimates, invokethe mechanical stabilization system to reject motions occurring within afirst operating bandwidth with an upper cutoff frequency. The processingapparatus 312 may be configured to, based on the sequence of orientationestimates, invoke the electronic image stabilization module to correctthe image for rotations of the image sensor occurring within a secondoperating bandwidth with a lower cutoff frequency to obtain a stabilizedimage. The lower cutoff frequency may be greater than the upper cutofffrequency. Thus the first operating bandwidth and the second operatingbandwidth may be non-overlapping so the mechanical stabilization systemand the electronic image stabilization module can operate independentlywithout substantial interference. In some implementations, theprocessing apparatus 312 may be configured to apply a first filter witha pass band matching the first operating bandwidth to the sequence oforientation estimates to obtain data that is input to the mechanicalstabilization system; and apply a second filter with a pass bandmatching the second operating bandwidth to the sequence of orientationestimates to obtain data that is input to the electronic imagestabilization module. For example, the first filter and the secondfilter may have transfer functions similar to those depicted in FIG. 7.By filtering the input to a mechanical stabilization system and anelectronic image stabilization module that have linear controllers, therespective operating bandwidths for these subsystems may be enforced. Insome implementations, the mechanical stabilization system includes aproportional integral derivative controller with coefficients tuned toenforce the first operating bandwidth. In some implementations, theelectronic image stabilization module includes a proportional integralderivative controller with coefficients tuned to enforce the firstoperating bandwidth. The processing apparatus 312 may be configured toadjust the first operating bandwidth and the second operating bandwidthin a complimentary manner by adjusting the upper cutoff frequency andthe lower cutoff frequency by a same amount. For example, the processingapparatus 312 may be configured to implement the process 600 of FIG. 6.

The image capture device 310 may include a user interface 320. Forexample, the user interface 320 may include an LCD display forpresenting images and/or messages to a user. For example, the userinterface 320 may include a button or switch enabling a person tomanually turn the image capture device 310 on and off. For example, theuser interface 320 may include a shutter button for snapping pictures.

The image capture device 310 may include a communications interface 322,which may enable communications with a personal computing device (e.g.,a smartphone, a tablet, a laptop computer, or a desktop computer). Forexample, the communications interface 322 may be used to receivecommands controlling image capture and processing in the image capturedevice 310. For example, the communications interface 322 may be used totransfer image data to a personal computing device. For example, thecommunications interface 322 may include a wired interface, such as ahigh-definition multimedia interface (HDMI), a universal serial bus(USB) interface, or a FireWire interface. For example, thecommunications interface 322 may include a wireless interface, such as aBluetooth interface, a ZigBee interface, and/or a Wi-Fi interface.

The image capture device 310 may include a battery 324 that powers theimage capture device 310 and/or its peripherals. For example, thebattery 324 may be charged wirelessly or through a micro-USB interface.

FIG. 3B is a block diagram of an example of a system 330 configured forimage capture with image stabilization. The system 330 includes an imagecapture device 340 and a personal computing device 360 that communicatevia a communications link 350. The image capture device 340 includes oneor more image sensors 342 that are configured to capture images. Theimage capture device 340 includes a communications interface 348configured to transfer images via the communication link 350 to thepersonal computing device 360. The personal computing device 360includes a processing apparatus 362 that is configured to receive, usingthe communications interface 366, images from the one or more imagesensors 342. The image capture device 340 includes gimbals and motors344 that are actuators of a mechanical stabilization system configuredto control an orientation of the one or more image sensors 342 (e.g., anorientation with respect to a movable platform). The gimbals and motors344 may be controlled by a controller of the mechanical stabilizationsystem, which may be implemented by the processing apparatus 362 (e.g.,as a software module or a specialized hardware module) and providecontrol signals to the motors 344 via the communication link 350. Theprocessing apparatus 362 may be configured to perform image signalprocessing (e.g., filtering, tone mapping, stitching, and/or encoding)to generate output images based on image data from the one or more imagesensors 342. The processing apparatus 362 may include an electronicimage stabilization module (e.g., implemented as a software module or aspecialized hardware module) configured to correct images for rotationsof the one or more image sensors 342. The image capture device 340includes one or more motion sensors 346 configured to detect motion ofthe one or more image sensors 342. The one or more motion sensors 346may provide feedback signals (e.g., via communication link 350) to themechanical stabilization system and/or electronic image stabilizationmodule. For example, the system 330 may be used to implement processesdescribed in this disclosure, such as the process 500 of FIG. 5 and theprocess 600 of FIG. 6.

The one or more image sensors 342 are configured to capture images. Theone or more image sensors 342 are configured to detect light of acertain spectrum (e.g., the visible spectrum or the infrared spectrum)and convey information constituting an image as electrical signals(e.g., analog or digital signals). For example, the one or more imagesensors 342 may include charge-coupled devices (CCD) or active pixelsensors in complementary metal-oxide-semiconductor (CMOS). The one ormore image sensors 342 may detect light incident through respective lens(e.g., a fisheye lens). In some implementations, the one or more imagesensors 342 include digital to analog converters. In someimplementations, the one or more image sensors 342 have respectivefields of view that overlap.

The processing apparatus 362 may include one or more processors havingsingle or multiple processing cores. The processing apparatus 362 mayinclude memory, such as random access memory device (RAM), flash memory,or any other suitable type of storage device such as a non-transitorycomputer readable memory. The memory of the processing apparatus 362 mayinclude executable instructions and data that can be accessed by one ormore processors of the processing apparatus 362. For example, theprocessing apparatus 362 may include one or more DRAM modules such asdouble data rate synchronous dynamic random-access memory (DDR SDRAM).In some implementations, the processing apparatus 362 may include adigital signal processor (DSP). In some implementations, the processingapparatus 362 may include an application specific integrated circuit(ASIC). For example, the processing apparatus 362 may include a customimage signal processor.

The processing apparatus 362 may include an electronic imagestabilization module configured to correct images for rotations of animage sensor. For example, the electronic image stabilization module mayimplemented by software executed by the processing apparatus 362. Theelectronic image stabilization module may take sensor data (e.g.,gyroscope data) and/or orientation estimates for the image sensor asinput, determine a corrective rotation, and apply the correctiverotation to an image from the image sensor to obtain a stabilized image.

The mechanical stabilization system for the one or more image sensors342 includes the gimbals and motors 344. The gimbals and motors 344 maybe parts of a movement mechanism (e.g., the movement mechanism 30). Thegimbals and motors 344 may connect the one or more image sensors 342 toa moving platform and control their orientation. For example, the imagecapture device 340 may include a drone that is coupled to a housing ofthe image sensor(s) 342 by the gimbals of the mechanical stabilizationsystem. The gimbals and motors 344 may span multiple axes (e.g., a3-axis gimbal set with brushless direct current motors). The mechanicalstabilization system may include a controller (e.g., a proportionalintegral derivative (PID) controller). For example, the controller ofthe mechanical stabilization system may be implemented by the processingapparatus 362 (e.g., as a software module or a specialized hardwaremodule).

The one or more motion sensors 346 are configured to detect motion ofthe one or more image sensors 342. For example, the one or more motionsensors 346 may include parts of an inertial measurement unit (e.g.,including gyroscopes, accelerometers, and/or magnetometers) that ismounted in a housing with the one or more image sensors 342. In someimplementations, the one or more motion sensors 346 may include parts ofan inertial measurement unit that is mounted in a movable platform ofthe image capture device 340. In some implementations, the one or moremotion sensors 346 include sensors (e.g., magnetic encoders, opticalencoders, and/or potentiometers) that detect the state of the gimbalsand motors 344 to measure a relative orientation of the image sensor anda movable platform of the image capture device 340. The processingapparatus 362 may be configured to determine a sequence of orientationestimates based on sensor data from the one or more motion sensors 346.For example, determining the sequence of orientation estimates mayinclude applying quadratic estimation to sensor data from a plurality ofthe one or more motion sensors 346.

The processing apparatus 362 may be configured to invoke the mechanicalstabilization system and the electronic image stabilization module incombination to mitigate distortion of captured images due to motion ofthe image capture device 340. The processing apparatus 362 may beconfigured to, based on the sequence of orientation estimates, invokethe mechanical stabilization system to reject motions occurring within afirst operating bandwidth with an upper cutoff frequency. The processingapparatus 362 may be configured to, based on the sequence of orientationestimates, invoke the electronic image stabilization module to correctthe image for rotations of the image sensor occurring within a secondoperating bandwidth with a lower cutoff frequency to obtain a stabilizedimage. The lower cutoff frequency may be greater than the upper cutofffrequency. Thus the first operating bandwidth and the second operatingbandwidth may be non-overlapping so the mechanical stabilization systemand the electronic image stabilization module can operate independentlywithout substantial interference. In some implementations, theprocessing apparatus 362 may be configured to apply a first filter witha pass band matching the first operating bandwidth to the sequence oforientation estimates to obtain data that is input to the mechanicalstabilization system; and apply a second filter with a pass bandmatching the second operating bandwidth to the sequence of orientationestimates to obtain data that is input to the electronic imagestabilization module. For example, the first filter and the secondfilter may have transfer functions similar to those depicted in FIG. 7.By filtering the input to a mechanical stabilization system and anelectronic image stabilization module that have linear controllers, therespective operating bandwidths for these subsystems may be enforced. Insome implementations, the mechanical stabilization system includes aproportional integral derivative controller with coefficients tuned toenforce the first operating bandwidth. In some implementations, theelectronic image stabilization module includes a proportional integralderivative controller with coefficients tuned to enforce the firstoperating bandwidth. The processing apparatus 362 may be configured toadjust the first operating bandwidth and the second operating bandwidthin a complimentary manner by adjusting the upper cutoff frequency andthe lower cutoff frequency by a same amount. For example, the processingapparatus 362 may be configured to implement the process 600 of FIG. 6.

The communications link 350 may be a wired communications link or awireless communications link. The communications interface 348 and thecommunications interface 366 may enable communications over thecommunications link 350. For example, the communications interface 348and the communications interface 366 may include a high-definitionmultimedia interface (HDMI), a universal serial bus (USB) interface, aFireWire interface, a Bluetooth interface, a ZigBee interface, and/or aWi-Fi interface. For example, the communications interface 348 and thecommunications interface 366 may be used to transfer image data from theimage capture device 340 to the personal computing device 360 for imagesignal processing (e.g., filtering, tone mapping, stitching, and/orencoding) to generate output images based on image data from the one ormore image sensors 342. For example, the communications interface 348and the communications interface 366 may be used to transfer motionsensor data from the image capture device 340 to the personal computingdevice 360 for processing in a controller of a mechanical stabilizationsystem and or an electronic image stabilization system. For example, thecommunications interface 348 and the communications interface 366 may beused to transfer control signals to the image capture device 340 fromthe personal computing device 360 for controlling the gimbals and motors344 of a mechanical stabilization system.

The personal computing device 360 may include a user interface 364. Forexample, the user interface 364 may include a touchscreen display forpresenting images and/or messages to a user and receiving commands froma user. For example, the user interface 364 may include a button orswitch enabling a person to manually turn the personal computing device360 on and off. In some implementations, commands (e.g., start recordingvideo, stop recording video, snap photograph, or select tracking target)received via the user interface 364 may be passed on to the imagecapture device 340 via the communications link 350.

FIG. 4 is a block diagram of an example of a system 400 configured forimage capture with image stabilization. The system includes an imagesensor 410 configured to capture an image; a mechanical stabilizationsystem 420 configured to control an orientation of the image sensor 410;an electronic image stabilization module 430 configured to correct theimage for rotations of the image sensor; and a motion tracking module440 including one or more motion sensors configured to detect motion ofthe image sensor 410 and provide input to the mechanical stabilizationsystem 420 and the electronic image stabilization module 430. Themechanical stabilization system 420 and the electronic imagestabilization module 430 may be configured to operate in substantiallynon-overlapping respective bandwidths. For example, the system 400 maybe used to implement processes described in this disclosure, such as theprocess 500 of FIG. 5 and the process 600 of FIG. 6.

The system 400 includes an image sensor 410 configured to capture animage 412. The image sensor 410 may be configured to detect light of acertain spectrum (e.g., the visible spectrum or the infrared spectrum)and convey information constituting an image as electrical signals(e.g., analog or digital signals). For example, the image sensor 410 mayinclude charge-coupled devices (CCD) or active pixel sensors incomplementary metal-oxide-semiconductor (CMOS). The image sensor 410 maydetect light incident through a lens (e.g., a fisheye lens). In someimplementations, the image sensor 410 includes a digital to analogconverter.

The system 400 includes a mechanical stabilization system 420, includingmotors, configured to control an orientation of the image sensor toreject motions occurring within a first operating bandwidth with anupper cutoff frequency. In this example, the mechanical stabilizationsystem 420 includes gimbals and motors 422 that are actuators used tocontrol an orientation of the image sensor 410 (e.g., an orientationwith respect to a movable platform). The gimbals and motors 422 may beparts of a movement mechanism (e.g., the movement mechanism 30). Thegimbals and motors 422 may connect the image sensor 410 to a movableplatform and control the orientation of the image sensor 410 with themovable platform. For example, the system 400 may include a drone (e.g.,the movable platform 40) that is coupled to a housing of the imagesensor 410 by the mechanical stabilization system 420. The gimbals andmotors 422 may span multiple axes (e.g., a 3-axis gimbal set withbrushless direct current motors). The mechanical stabilization system420 may include a controller 424 (e.g., a proportional integralderivative (PID) controller). For example, the controller 424 of themechanical stabilization system 420 may be implemented as a softwaremodule or a specialized hardware module (e.g., by the processingapparatus 312). The controller 424 may take targeting input 426 from atracking system (e.g., the tracking system 60), such a set point or adesired orientation. The controller 424 may be configured to rejectionmotions occurring within the first operating bandwidth that deviate froma desired orientation (e.g., a current orientation). The gimbals andmotors 422 are used to generate forces 428 (e.g., torques ordisplacements) to actuate control of an orientation and/or position ofthe image sensor 410. For example, the forces 428 may serve to keep theimage sensor pointed steadily at target while a connected movableplatform (e.g., a drone) is moving.

The system 400 includes an electronic image stabilization module 430configured to correct images for rotations of the image sensor 410occurring within a second operating bandwidth with a lower cutofffrequency to obtain a stabilized image 432. The lower cutoff frequencyof the second operating bandwidth is greater than the upper cutofffrequency of the first operating bandwidth. Having substantiallynon-overlapping operating bandwidths may prevent or reduce interferencebetween the dynamics of the mechanical stabilization system 420 and thedynamics of the electronic image stabilization module 430 and improveimage quality of the stabilized image 432. For example, the electronicimage stabilization module 430 may implemented by software executed by aprocessing apparatus (e.g., an image signal processor). The electronicimage stabilization module 430 may take sensor data (e.g., gyroscopedata) and/or orientation estimates for the image sensor as input 434,determine a corrective rotation, and apply the corrective rotation tothe image 412 from the image sensor 410 to obtain a stabilized image432. For example, certain higher frequency motions of the image sensor410 (e.g., vibrations) may be too fast to be efficiently rejected by themechanical stabilization system 420 and thus may cause distortion of theimage 412. This remaining distortion may be corrected in whole or inpart by digital image processing in the electronic image stabilizationmodule 430.

The system 400 includes a motion tracking module 440 including one ormore motion sensors configured to detect motion of the image sensor 410and determine a sequence of orientation estimates for the image sensor410. The motion tracking module 440 includes an inertial measurementunit 442 that can be used to detect changes in position and orientationof the image sensor 410. For example, the inertial measurement unit 442may include a 3-axis accelerometer, a 3-axis gyroscope, and/or a 3-axismagnetometer. The motion tracking module 440 includes encoders 444(e.g., magnetic encoders, optical encoders, and/or interferometric laserencoders) that can be used to detect a position and/or orientation ofthe image sensor 410 relative to movable platform (e.g., a drone)connected by the gimbals and motors 422. The motion tracking module 440includes potentiometers 446 that detect a state of the gimbals andmotors 422 and thus a position and/or orientation of the image sensor410 relative to movable platform (e.g., a drone) connected by thegimbals and motors 422. The motion tracking module 440 may include asensor fusion module for combining data from the various sensors of themotion tracking module to determine the sequence of estimates of theposition and/or orientation of the image sensor 410. For example,determining the sequence of orientation estimates may include applyingquadratic estimation to sensor data from the inertial measurement unit442, the encoders 444 and/or the potentiometers 446.

The system 400 includes a first filter module 450 for the mechanicalstabilization system 420. The first filter module 450 is configured toapply a first filter with a pass band matching the first operatingbandwidth to a sequence of orientation estimates 452 to obtain data 454that is input to mechanical stabilization system 420. For example, thefirst filter may have a transfer function similar to the transferfunction 710 illustrated in FIG. 7. The first operating bandwidth forthe mechanical stabilization system 420 may be configured by takinginput data 454 from the first filter module 450, where the controller424 is a linear system. It is worth noting that he first operatingbandwidth configured by taking input data 454 from the first filtermodule 450 may be a narrower subset of a maximum operating bandwidth ofthe mechanical stabilization system 420 (e.g., limited by factors suchas the maximum torque of the motors 422). In some implementations (notshown in FIG. 4), the first operating bandwidth of the mechanicalstabilization system 420 is configured or enforced by tuning thecontroller 424. For example, the first filter module 450 may beimplemented as software executed by a processing apparatus (e.g., theprocessing apparatus 312).

The system 400 includes a second filter module 460 for the electronicimage stabilization module 430. The second filter module 460 isconfigured to apply a second filter with a pass band matching the secondoperating bandwidth to a sequence of orientation estimates 462 to obtaindata that is input 434 to electronic image stabilization module 430. Forexample, the second filter may have a transfer function similar to thetransfer function 720 illustrated in FIG. 7. The second operatingbandwidth for the electronic image stabilization module 430 may beconfigured by taking input 434 from the second filter module 460, wherea controller of the electronic image stabilization module 430 is alinear system. It is worth noting that he second operating bandwidthconfigured by taking input 434 from the second filter module 460 may bea narrower subset of a maximum operating bandwidth of the electronicimage stabilization module 430 (e.g., limited by factors such as tuningof a controller). In some implementations (not shown in FIG. 4), thesecond operating bandwidth of the electronic image stabilization module430 is configured or enforced by tuning a controller of the electronicimage stabilization module 430. For example, the second filter module460 may be implemented as software executed by a processing apparatus(e.g., the processing apparatus 312).

FIG. 5 is a flowchart of an example of a process 500 for image capturewith mechanical and electronic image stabilization. The process 500includes adjusting 510 respective operating bandwidths of a mechanicalstabilization system and an electronic image stabilization module in acomplimentary manner; determining 520 a sequence of orientationestimates based on sensor data from one or more motion sensors; based onthe sequence of orientation estimates, invoking 530 a mechanicalstabilization system to reject motions of an image sensor occurringwithin a first operating bandwidth with an upper cutoff frequency;receiving 540 an image from the image sensor; based on the sequence oforientation estimates, invoking 550 an electronic image stabilizationmodule to correct the image for rotations of the image sensor occurringwithin a second operating bandwidth with a lower cutoff frequency toobtain a stabilized image, wherein the lower cutoff frequency is greaterthan the upper cutoff frequency; and storing, displaying, ortransmitting 560 an output image based on the stabilized image. Forexample, the process 500 may be implemented by the movable imagingsystem 10 of FIG. 1, the system 300 of FIG. 3A, the system 330 of FIG.3B, or the system 400 of FIG. 4. For example, the process 500 may beimplemented by an image capture device, such the image capture device310 shown in FIG. 3A. For example, the process 500 may be implemented bya personal computing device, such as the personal computing device 360.

The process 500 includes adjusting 510 the first operating bandwidth andthe second operating bandwidth in a complimentary manner by adjustingthe upper cutoff frequency and the lower cutoff frequency by a sameamount. The operating bandwidths of the two systems may be adjusted 510to manage tradeoffs between costs and performance benefits of operatingthe mechanical stabilization system with a wide operating bandwidth. Forexample, running motors of the mechanical stabilization system with awide operating bandwidth may consume more power and generate excessiveheat. On the other hand, operating the mechanical stabilization systemwith a wide operating bandwidth may achieve better image quality thanrelying more on the electronic image stabilization module, which may beunable to correct some components of distortion (e.g., blurring)resulting from the motion of the image sensor. For example, the firstoperating bandwidth and the second operating bandwidth may be adjusted510 dynamically based on a mode selection made by a user of an imagecapture device, a condition of the environment (e.g., low light, or highcontrast), a temperature of the motors, and/or a state of charge of abattery of the image capture device. For example, the first operatingbandwidth and the second operating bandwidth may be adjusted 510 byimplementing the process 600 of FIG. 6. In some implementations, thefirst operating bandwidth and the second operating bandwidth may beadjusted 510 by changing filters applied to the motion signals input tothe mechanical stabilization system and the electronic imagestabilization module respectively. In some implementations, the firstoperating bandwidth and the second operating bandwidth may be adjusted510 by tuning parameters (e.g., coefficients of a PID controller) ofrespective controllers of the mechanical stabilization system and theelectronic image stabilization module.

The process 500 includes determining 520 a sequence of orientationestimates based on sensor data from one or more motion sensors (e.g.,the one or more motion sensors 318). The one or more motion sensors mayinclude an inertial measurement unit (e.g., the inertial measurementunit 442) that can be used to detect changes in position and orientationof the image sensor. The one or more motion sensors may include encoders(e.g., magnetic encoders, optical encoders, and/or interferometric laserencoders) that can be used to detect a position and/or orientation ofthe image sensor relative to movable platform (e.g., a drone) connectedby the gimbals and motors of the mechanical stabilization system. Theone or more motion sensors may include potentiometers that detect astate of the gimbals and motors and thus a position and/or orientationof the image sensor relative to a movable platform (e.g., a drone)connected by the gimbals and motors. Data from the one or more motionsensors may be combined to determine 520 the sequence of estimates ofthe orientation of the image sensor. For example, determining 520 thesequence of orientation estimates may include applying quadraticestimation to sensor data from the one or more motion sensors.

The process 500 includes, based on the sequence of orientationestimates, invoking 530 a mechanical stabilization system (e.g., themechanical stabilization system 420) to reject motions of the imagesensor occurring within a first operating bandwidth with an upper cutofffrequency. For example, the mechanical stabilization system may includegimbals and motors (e.g., the gimbals and motors 316) controlled byproportional integral derivative (PID) controllers. For example, themechanical stabilization system may be invoked 530 by calling and/orexecuting a software implementation of a controller of the mechanicalstabilization system and causing it to process input data, based on thesequence of orientation estimates, to generate control signals to driveactuators (e.g., the gimbals and motors 316) to control the orientationand/or position of the image sensor. For example, the mechanicalstabilization system may be invoked 530 by inputting data, based on thesequence of orientation estimates, to a specialized hardwareimplementation of a controller of the mechanical stabilization systemand causing it to process the input data to generate control signals todrive actuators (e.g., the gimbals and motors 316) to control theorientation and/or position of the image sensor. In someimplementations, the data input to the mechanical stabilization systemis filtered to enforce the first operating bandwidth on a linearcontroller. For example, a first filter (e.g., with a transfer functionsimilar to the transfer function 710 illustrated in FIG. 7) with a passband matching the first operating bandwidth may be applied to thesequence of orientation estimates to obtain data that is input to themechanical stabilization system. Invoking 530 the mechanicalstabilization system may reduce undesired motion of the image sensor andassociated distortions (e.g., blurring and shaking between frames ofvideo).

The process 500 includes receiving 540 an image from the image sensor.The image sensor may be part of an image capture system (e.g., themovable imaging system 10, the image capture device 310, or the imagecapture device 340). In some implementations, the image sensor may beattached to a processing apparatus that implements the process 500. Forexample, the image may be received 540 from the image sensor via a bus.In some implementations, the image may be received 540 via acommunications link (e.g., the communications link 350). For example,the image may be received 540 via a wireless or wired communicationsinterface (e.g., Wi-Fi, Bluetooth, USB, HDMI, Wireless USB, Near FieldCommunication (NFC), Ethernet, a radio frequency transceiver, and/orother interfaces). For example, the image may be received 540 viacommunications interface 366. For example, the image may be received 540as an input image signal, which may represent each pixel value in adefined format, such as in a RAW image format. In some implementations,the image may be frame of video, i.e., one of a sequence of images of avideo. In some implementations, the image is received 540 directly fromthe image sensor without intermediate image processing. In someimplementations, the image is received 540 after being subjected tointermediate image processing (e.g., correction of dead pixels, bandprocessing, decoupling of vertical blanking, spatial noise reduction,and/or temporal noise reduction).

The process 500 includes, based on the sequence of orientationestimates, invoking 550 an electronic image stabilization module (e.g.,the electronic image stabilization module) to correct the image forrotations of the image sensor occurring within a second operatingbandwidth with a lower cutoff frequency to obtain a stabilized image.The lower cutoff frequency may be greater than the upper cutofffrequency, so that the first operating bandwidth and the secondoperating bandwidth are substantially non-overlapping. For example, theelectronic image stabilization module may be invoked 550 by callingand/or executing a software implementation of the electronic imagestabilization module and causing it to process input data, based on thesequence of orientation estimates, to determine and apply a correctiverotation transformation to the image from the image sensor to stabilizethe image (e.g., with respect to other images in sequence of frames ofvideo). For example, the electronic image stabilization module may beinvoked 550 by inputting data, based on the sequence of orientationestimates, to a specialized hardware implementation of the electronicimage stabilization module and causing it to process the input data todetermine and apply a corrective rotation transformation to the imagefrom the image sensor to stabilize the image. In some implementations,the data input to the electronic image stabilization module is filteredto enforce the second operating bandwidth on a linear controller. Forexample, a second filter (e.g., with a transfer function similar to thetransfer function 720 illustrated in FIG. 7) with a pass band matchingthe second operating bandwidth may be applied to the sequence oforientation estimates to obtain data that is input to the electronicimage stabilization module. Having substantially non-overlappingoperating bandwidths may prevent or reduce interference between thedynamics of the mechanical stabilization system and the dynamics of theelectronic image stabilization module and improve image quality of thestabilized image. For example, certain higher frequency motions of theimage sensor (e.g., vibrations) may be too fast to be efficientlyrejected by the mechanical stabilization system and thus may causedistortion of the image. This remaining distortion may be corrected inwhole or in part by digital image processing in the electronic imagestabilization module.

The process 500 includes storing, displaying, or transmitting 560 anoutput image based on the stabilized image. In some implementations, theoutput image is the stabilized image. In some implementations, thestabilized image may by subject to additional image processing (e.g.,perceptual tone mapping, lens distortion correction, electronic rollingshutter correction, stitching with parallax correction and blending tocombine images from multiple image sensors, and/or output projection) todetermine the output image. For example, the output image may betransmitted 560 to an external device (e.g., a personal computingdevice) for display or storage. For example, the output image may bestored 560 in memory of a processing apparatus (e.g., the processingapparatus 312 or the processing apparatus 362). For example, the outputimage may be displayed 560 in the user interface 320 or in the userinterface 364. For example, the output image may be transmitted 560 viathe communications interface 322.

FIG. 6 is a flowchart of an example of a process 600 for adjusting theoperating bandwidths of a mechanical stabilization system and anelectronic image stabilization module. The process 600 includesreceiving 610 a mode selection input from a user interface; adjusting620 the upper cutoff frequency and the lower cutoff frequency based onthe mode selection input; detecting 630 a condition of the environment;adjusting 640 the upper cutoff frequency and the lower cutoff frequencybased on the condition; determining 650 a temperature of the motors ofthe mechanical stabilization system; adjusting 660 the upper cutofffrequency and the lower cutoff frequency based on the temperature;determining 670 a state of charge of a battery; and adjusting 680 theupper cutoff frequency and the lower cutoff frequency are based on thestate of charge. For example, the process 600 may be implemented by themovable imaging system 10 of FIG. 1, the system 300 of FIG. 3A, thesystem 330 of FIG. 3B, or the system 400 of FIG. 4. For example, theprocess 600 may be implemented by an image capture device, such theimage capture device 310 shown in FIG. 3A. For example, the process 600may be implemented by a personal computing device, such as the personalcomputing device 360.

The process 600 includes receiving 610 a mode selection input from auser interface (e.g., the user interface 320 or the user interface 364).For example, the user mode selection may be based on a user pressing amode button or icon. For example, the mode selection input may specify ahigh image quality mode or a low image quality mode. For example, theuser mode selection may be based on a user sliding a wipe bar tomanually adjust an image quality level within a range of discretevalues. For example, the user mode selection may specify other cameramodes, such as a frame rate or shutter speed.

The process 600 includes adjusting 620 the upper cutoff frequency andthe lower cutoff frequency based on the mode selection input. Forexample, the upper cutoff frequency and the lower cutoff frequency maybe increased based on a mode selection input specifying a high imagequality mode. For example, the upper cutoff frequency and the lowercutoff frequency may be decreased based on a mode selection inputspecifying a low image quality mode. For example, the upper cutofffrequency and the lower cutoff frequency may be shifted by an amountthat is proportional to a change in image quality level indicated by amode selection input. For example, the upper cutoff frequency and thelower cutoff frequency may be increased based on a mode selection inputspecifying a low frame rate or a low shutter speed.

The process 600 includes detecting 630 a condition of an environmentviewed by the image sensor. Dynamic environment may be taken intoaccount such that low light, high motion, high noise, and high contrastmoments can dynamically rely more on the mechanical stabilization systemand less on the electronic image stabilization module. For example, thecondition may be selected from the group consisting of low light, highmotion, high noise, and high contrast.

The process 600 includes adjusting 640 the upper cutoff frequency andthe lower cutoff frequency based on the condition. For example, theupper cutoff frequency and the lower cutoff frequency may be increasedbased on detected 630 condition indicating low light, high motion, highnoise, or high contrast.

The process 600 includes determining 650 a temperature of motors of themechanical stabilization system. Temperature of motors may be determined650 by direct measurement or by indirect estimation with models. In adirect measurement technique a sensor such as a thermistor may beutilized to sample motor temp. In some implementations, a thermodynamicmodel of the motors is used to estimate the motor temperature based onambient temp or a worst case fixed value such as the maximum guaranteedoperational ambient temp in combination with a calculation. Thecalculation may be achieved by a motor controller sampling the currentthat is applied to the motor and roughly treating it as a thermal lossand calculating power into the motor as I{circumflex over ( )}2*R whereR is the resistance of the motor and I is the current. A model may beused for each motor/structure and a lookup table or curve fit for thealgorithm to reference. For example, determining 650 the temperature mayinclude receiving measurements of current drawn by the motors of themechanical stabilization system, and estimating the temperature based onthe measurements of current.

The process 600 includes adjusting 660 the upper cutoff frequency andthe lower cutoff frequency based on the temperature. Reducing the uppercutoff frequency and the lower cutoff frequency and thus reducing thefirst operation bandwidth of the mechanical stabilization system maycause less power to be applied to the motors and thus cool the motorsover time. The determined 650 temperature of the motors may be comparedto a maximum rated temperature for the motors and the first bandwidthmay be reduced if the temperature is too close or over the maximum ratedtemperature by an amount that may depend on the temperature. In someimplementations, the upper cutoff frequency and the lower cutofffrequency are adjusted 660 based on a difference between the temperatureand a maximum rated temperature for the motors of the mechanicalstabilization system. For example, the upper cutoff frequency of themechanical stabilization system may be adjusted 660 according to:MSS_CF=(((M_T−t)+B)*S_F)+MSS_MIN_CF)Where MSS_CF is the upper cutoff frequency of the mechanicalstabilization system, M_T is the maximum rated temperature of themotors, t is the determined 650 temperature, B is a constant bias term,S_F is a constant scale factor, and MSS_MIN_CF is a minimum value of theupper cutoff frequency of the mechanical stabilization system. The lowercutoff frequency of the electronic image stabilization module may alsobe adjusted using a similar equation with a different offset value(e.g., EIS_MIN_CF instead of MSS_MIN_CF).

The process 600 includes determining 670 a state of charge of a battery.An integrated battery tester may be used to measure and/or estimate astate of charge of the battery (e.g., based on a sequence ofperiodically sampled voltage measurements of the battery).

The process 600 includes adjusting 680 the upper cutoff frequency andthe lower cutoff frequency based on the state of charge. Reducing theupper cutoff frequency and the lower cutoff frequency and thus reducingthe first operation bandwidth of the mechanical stabilization system maycause less power to be applied to the motors and thus conserves batterycharge. The determined 670 state of charge may be compared to a minimumcharge level (e.g., 10% charged) and the first bandwidth may be reducedif the state of charge is too close or under the minimum charge level byan amount that may depend on the state of charge. In someimplementations, the upper cutoff frequency and the lower cutofffrequency are adjusted 680 based on a difference between the state ofcharge and a minimum charge level for the battery. For example, theupper cutoff frequency of the mechanical stabilization system may beadjusted 680 according to:MSS_CF=(((s−MIN_CL)+B)*S_F)+MSS_MIN_CF)

Where MSS_CF is the upper cutoff frequency of the mechanicalstabilization system, M_T is the maximum rated temperature of themotors, s is the determined 670 state of charge, B is a constant biasterm, S_F is a constant scale factor, and MSS_MIN_CF is a minimum valueof the upper cutoff frequency of the mechanical stabilization system.The lower cutoff frequency of the electronic image stabilization modulemay also be adjusted using a similar equation with a different offsetvalue (e.g., EIS_MIN_CF instead of MSS_MIN_CF).

FIG. 7 is a plot 700 of an example of a transfer function 710 of an MSSfilter, corresponding to the operating bandwidth of the MSS, overlaidwith a transfer function 720 of an EIS filter, corresponding to theoperating bandwidth of the EIS. The plot 700 shows filter gain on y axisand frequency on the x axis. The transfer function 710 of the MSS filterhas an upper cutoff frequency 730. The transfer function 720 of the EISfilter has a lower cutoff frequency 740. A first bandwidth 750 is theoperating bandwidth of the corresponding mechanical stabilizationsystem. A second bandwidth 760 is the operating bandwidth of thecorresponding electronic image stabilization module. The lower cutofffrequency 740 is greater than the upper cutoff frequency 730, so thatthe first bandwidth 750 and the second bandwidth 760 are substantiallynon-overlapping.

It should be noted that the processes described in relation to FIGS. 5-6and similar processes may be applied to multiple images from differentimage sensors of an image capture apparatus (e.g., the movable imagingassembly 20 shown in FIG. 1, the system 300 of FIG. 3A, or the system330 of FIG. 3B). The resulting stabilized images may be combined using astitching operation.

In some implementations, a mechanical stabilization system may beintegrated in an image capture module (e.g., the image capture module800 describe below) that includes an image sensor. A movable platformfor image capture may be a handheld module, such as the handheld module900 described below, that attaches to an image capture module to form amovable imaging assembly 1000 as described in relation to FIGS. 10A-B.For example, process 500 of FIG. 5 may be implemented by the movableimaging assembly 1000. For example, process 600 of FIG. 6 may beimplemented by the movable imaging assembly 1000.

FIGS. 8A and 8B are pictorial illustrations of an example of an imagecapture module 800 from two perspectives. The image capture module 800includes an image sensor 810 configured to capture images; a mechanicalstabilization system 820, including gimbals and motors (822, 824, and826); and a connector 830 configured to interchangeably connect themechanical stabilization system to an aerial vehicle (e.g., a quadcopterdrone) and a handheld module (e.g., the handheld module 900).

The image capture module 800 includes an image sensor 810 configured tocapture images (e.g., still images or frames of video). The image sensor810 may be configured to detect light of a certain spectrum (e.g., thevisible spectrum or the infrared spectrum) and convey informationconstituting an image as electrical signals (e.g., analog or digitalsignals). For example, the image sensor 810 may include charge-coupleddevices (CCD) or active pixel sensors in complementarymetal-oxide-semiconductor (CMOS). The image capture module 800 includesa lens 812 (e.g., a wide-angle rectilinear lens). The image sensor 810detects light from the environment that is incident through the lens812.

The image capture module 800 may also include a processing apparatus(e.g., including memory, an image signal processor, a hardware encoder,a microcontroller, and/or other processor) that is configured to track auser based on position data from a beacon module and/or based oncomputer vision tracking of the user in images from the image sensor 810in a first usage scenario, where the image capture module 800 isattached to an aerial vehicle (e.g., a quadcopter drone), and/or in asecond usage scenario, where the image capture module 800 is attached toan handheld module (e.g., the handheld module 900). In someimplementations, the processing apparatus may be configured to performimage processing operations (e.g., correction of dead pixels, bandprocessing, decoupling of vertical blanking, spatial noise reduction,temporal noise reduction, automatic white balance, global tone mapping,local tone mapping, lens distortion correction, electronic rollingshutter correction, electronic image stabilization, output projection,and/or encoding) on images captured by the image sensor 810. In someimplementations, some or all of the image processing operations areperformed on the images captured by the image sensor by a processingapparatus that is located in whole or in part in another component of alarger movable imaging system 10. For example, the processing apparatusmay be located inside the connector 830 below the gimbal 826 of themechanical stabilization system 820.

The image capture module 800 includes a mechanical stabilization system820, including gimbals and motors (822, 824, and 826) (e.g.,corresponding to pitch, yaw, and roll respectively), that is integratedwith the image sensor 810 in the image capture module 800 and configuredto control an orientation of the image sensor 810. For example, thegimbals and motors (822, 824, and 826) may enable rotation of the imagesensor with three degrees of freedom. In some implementations, thegimbals and motors (822, 824, and 826) respectively enable a wide rangeof rotation angles (e.g., up to 180 degrees, 270 degrees or 360degrees). A gimbal 826 of the mechanical stabilization system 820 issubstantially flush with a surface of the connector 830 causing themechanical stabilization system 820 to have a low profile and protectthe gimbal 826 from damage. In some implementations, the gimbal 826 iscontained entirely within a body of the connector 830, at or below thegrade of an outer surface of the connector 830. For example, themechanical stabilization system 820 may be controlled with a controller(e.g., a proportional integral derivative controller) based on targetorientations determined by a processing apparatus based on image datafrom the image sensor 810, motion sensor data from a motion sensor inthe image capture module 800 or a movable platform (e.g., a quadcopterdrone or the handheld module 900) to which the image capture module 800module is attached, and/or position data for a tracking target from abeacon.

The mechanical stabilization system 820 may be configured to enable anelectronically actuated transport mode. When many 3-axis gimbals arepowered off they simply float around aimlessly and are cumbersome to putaway or transport. In some implementations, the mechanical stabilizationsystem 820 is configured to enable an electronically actuated transportmode in which: upon the occurrence of triggering event (e.g., aspecialized user command or a command to power OFF the image capturemodule 800 or the mechanical stabilization system 820, each of thegimbals and motors (822, 824, and 826) are electronically controlled toassume a fold-flat position and maintain that position for a fixed timeperiod (e.g., 10, 30, or 60 seconds), allowing the user to easily slipthe image capture module 800 into a pocket, carrying case, backpack, orother container. After the time has expired, the mechanicalstabilization system 820 will completely power OFF allowing the gimbalarms to move freely, once in the desired transport location. In someimplementations, this electronically actuated transport mode can beaccompanied by a physical lock which is either integrated into thegimbal itself, or via an external means such as a bracket or carryingcase. For example, the electronically actuated transport mode may beimplemented using electronic motor position sensors, mechanicalfold-flat ability (range-of-motion), and firmware control (e.g.,implemented in a processing apparatus of the image capture module 800).

The image capture module 800 includes a connector 830 configured tointerchangeably connect the mechanical stabilization system 820 to anaerial vehicle (e.g., a quadcopter drone) in a first usage scenario anda handheld module in a second usage scenario (e.g., the handheld module900). The connector may be keyed to a slot of the aerial vehicle andkeyed to a slot of the handheld module. The connector 830 is keyed byvirtue of the shape of an outer surface of the connector 830, which isfitted to the corresponding shape of the slot in the aerial vehicle andthe corresponding shape in the slot of the handheld module (e.g., thehandheld module 900). The keyed shape of the connector 830 includes someasymmetry (i.e., the rectangular cross-section of the connector 830 thatnarrows, sloping inward, about half way down the connector 830 on oneside), which may facilitate easy connection of the aerial vehicle andthe handheld module to the image capture module 800 by preventing a userfrom accidentally inserting the connector 830 in an improperorientation. For example, the connector 830 may include a firstfastening mechanism and a second fastening mechanism configured tosecure the connector 830 when the image capture module 800 is attachedto the handheld module. The fastening mechanisms may be configured suchthat either of the first fastening mechanism and second fasteningmechanism is sufficient to secure the connector 830. The connector 830includes an electrical connector (e.g., a universal serial bus (USB)type C connector) nested inside of the keyed outer portion of theconnector 830. The electrical connector may include multiple conductorsthat can be used to provide power from a movable platform (e.g., thehandheld module 900) to the image capture module 800 and transfercommunication signals (e.g., USB 2.0, USB 3.0, I2C, SPI, and/or MIPIsignals) between the movable platform and the image capture module 800when they are connected. In some implementations, the connector 830includes pairs of conductors respectively used to transfer power to theimage capture module 800, bulk transfer data from the image capturemodule 800, transfer control signals to the image capture module 800,and transfer real-time video data from the image capture module 800.

The connector may include an electrical connector (e.g., a universalserial bus (USB) type C connector) nested inside of the keyed outerportion of the connector. The electrical connector may include multipleconductors that can be used to provide power from the handheld module900 to the image capture module 800 and transfer communication signals(e.g., USB 2.0, USB 3.0, I2C, SPI, and/or MIPI (Mobile IndustryProcessor Interface) signals) between the handheld module 900 and theimage capture module 800 when they are connected. For example,conductors of the connection may be used to transfer power, high-speedbulk data transfers, real-time embedded control signaling, and/or rawvideo signals at a capture frame rate. For example, the connector mayinclude pairs of conductors respectively used to transfer power to theimage capture module 800, bulk transfer data from the image capturemodule 800, transfer control signals to the image capture module 800,and transfer real-time video data from the image capture module 800.

In the example of FIGS. 8A and 8B, the gimbal 826 of the mechanicalstabilization system 820 is substantially flush with a surface of theconnector 830. The gimbal 826 may be protected by a body of theconnector 830 to protect the gimbal from damage and/or the ingress ofdust. For example, gimbal 826 may be a roll gimbal and with acorresponding roll motor with a roll motor housing that is built intothe housing of the connector 830 so that the roll motor housing sitsbelow the grade of an outer surface of the connector 830 and is hiddenand/or protected. This configuration may provide advantages over othermechanical stabilization systems with all of their gimbals exposed(e.g., three axis gimbals exposed, including a roll axis motor housingsitting on top of a main housing). For example, locating the gimbal 826within the connector 830 and/or substantial flush with a surface of theconnector 830 may reduce amount of exposed gimbal parts, reduce heightof gimbal above a main housing, and/or simplify the overall design byreducing the number visible motor elements (e.g., from three gimbals twogimbals).

FIGS. 9A and 9B are pictorial illustrations of an example of a handheldmodule 900 from two perspectives. The handheld module 900 includes adisplay 910, a record button 920, a status indicator light 924, a firstfastening mechanism 930 and a second fastening mechanism 932, a slot 940with a shape matched to the connector 830 of the image capture module800, and a battery cover 950 with a battery release latch 952.

The handheld module 900 may be shaped such that it may be ergonomicallyheld in a hand during use while operating a touch display and/or abutton (e.g., the record button 920) of the handheld module 900. Theouter material may be selected to have a rubbery grip texture.

The handheld module 900 includes a user interface that allows a user tocontrol image capture with an attached image capture module (e.g., theimage capture module 800). The user interface includes the display 910for viewing captured images, the record button 920 for snapping stillimages or starting or stopping recording of video, and the statusindicator light 924. The status indicator light 924 may include amulti-color LED device and may reflect the status of an electronicconnection to an attached image capture module and/or a recording state.In some implementations, the display 910 is a touch-screen that enablesthe input of additional commands by a user. For example, a user mayinput commands to change a gimbal angle; enter “selfie-mode,” or“HiLight Tag” by voice command and/or input received via the touchinterface of the display 910 and/or a button of the handheld module 900.A “selfie-mode” function may rotate the gimbal 826 (e.g., rotate 180degrees), such that an image sensor (e.g., the image sensor 810) facesthe same direction as the display 910. A “HiLight Tag” function mayenable a user to mark an image or frames of video as significant withmetadata. For example, a “HighLight Tag” gesture may be defined for atouch screen interface of the display 910, which may enable a user togenerate portions of a video data temporally and/or spatially byspecifying an object or other portions of a frame as frames aredisplayed on the display 910.

The first fastening mechanism 930 and the second fastening mechanism 932are configured to secure the connector 830 of the image capture module800 when it is inserted in the slot 940 to attach the handheld module900 to the image capture module 800. The first fastening mechanism 930and the second fastening mechanism 932 include a button and a slider,respectively, that may be used to disengage the first fasteningmechanism 930 and the second fastening mechanism 932 in order todisconnect from and attached image capture module (e.g., the imagecapture module 800). Other types of fastening mechanisms are alsopossible.

The battery cover 950 may be opened using the battery release latch 952to access a battery of the handheld module 900 for replacement orrecharging. For example, multiple batteries may be used and swapped intothe handheld module 900 to enable continued use while one of thebatteries is charged in an external charger.

FIG. 10A is a pictorial illustration of an example of a handheld module900 oriented to be connected to an image capture module 800 to form amovable imaging assembly 1000. The connector 830 of the image capturemodule 800 is keyed to the slot 940 of the handheld module 900. From theillustrated orientation, the image capture module 800 may be moved downto slide the connector 830 into the slot 940 to attach the image capturemodule 800 to the handheld module 900 to form the movable imagingassembly 1000. When the connector 830 is inserted into the slot 940,paired fastening mechanisms (e.g., latches) in the connector 830 and theslot 940 may engage to secure the newly formed connection. For example,spring loaded latches may engage to secure the connection of the movableimaging assembly 1000. As part of the connection, mated electronicconnectors (e.g., USB Type C connectors) nested in the connector 830 andthe slot 940 may engage to form an electronic connection includingmultiple conductors, which may be used to supply power from the handheldmodule 900 to image capture module 800 and to transfer control signalsand data (e.g., image data) between the attached modules of the movableimaging assembly 1000.

When a user seeks to disconnect the handheld module 900 from the imagecapture module 800, they may release these fastening mechanisms. Forexample, latches may be manually released by a user using their fingerson buttons or release levers. In some implementations, two latches mustbe simultaneously released in order to disconnect the handheld module900 from the image capture module 800, which may reduce the risk ofaccidental disconnection. For example, a cycle of connecting anddisconnecting the handheld module 900 from the image capture module 800may only take a few seconds for a user to complete.

FIG. 10B is a pictorial illustration of an example of a movable imagingassembly 1000 in communication with a personal computing device 1020. Inthe usage scenario of FIG. 10B, the movable imaging assembly 1000 isheld in a hand 1010 of a user and is capturing images (e.g., stillimages or frames of video) of the user. The captured images aredisplayed on the display 910 of the handheld module 900. The capturedimages may be transferred to the personal computing device 1020 (e.g., asmartphone) via a wireless link 1025 (e.g., using a Bluetooth link or aWiFi link). The personal computing device 1020 may then be used todisplay and/or share or otherwise transmit and distribute the capturedimages. The personal computing device 1020 may also be configured withan application that may be used to remotely control image capturefunctions of the movable imaging assembly 1000 and/or update softwareinstalled on a processing apparatus of the movable imaging assembly1000.

In this example, a gimbal 826 of the mechanical stabilization system issubstantially flush with a surface (e.g., the top surface) of thehandheld module 900 when the image capture module 800 is attached to thehandheld module 900. This may result in the mechanical stabilizationsystem and the image sensor having a low profile and protecting thegimbal 826 to reduce risk of damage to the gimbal 826. Thisconfiguration may provide advantages over other mechanical stabilizationsystems with all of their gimbals exposed (e.g., three axis gimbalsexposed, including a roll axis motor housing sitting on top of a mainhousing). For example, locating the gimbal 826 within the handheldmodule 900 and/or substantial flush with a surface of the handheldmodule 900 when the image capture module 800 is attached to the handheldmodule 900 may reduce amount of exposed gimbal parts, reduce height ofgimbal above a main housing, and/or simplify the overall design byreducing the number visible motor elements (e.g., from three gimbals twogimbals).

A first implementation is an system that includes: an image sensorconfigured to capture an image; one or more motion sensors configured todetect motion of the image sensor; a mechanical stabilization system,including gimbals and motors, configured to control an orientation ofthe image sensor; an electronic image stabilization module configured tocorrect images for rotations of the image sensor; and a processingapparatus that is configured to: determine a sequence of orientationestimates based on sensor data from the one or more motion sensors;based on the sequence of orientation estimates, invoke the mechanicalstabilization system to reject motions occurring within a firstoperating bandwidth with an upper cutoff frequency; receive the imagefrom the image sensor; based on the sequence of orientation estimates,invoke the electronic image stabilization module to correct the imagefor rotations of the image sensor occurring within a second operatingbandwidth with a lower cutoff frequency to obtain a stabilized image,wherein the lower cutoff frequency is greater than the upper cutofffrequency; and store, display, or transmit an output image based on thestabilized image. The first implementation may include a handheld modulethat is coupled to a housing of the image sensor by the gimbals of themechanical stabilization system, wherein the handheld module includes abattery and an integrated display configured to display images receivedfrom the image sensor.

While the disclosure has been described in connection with certainembodiments, it is to be understood that the disclosure is not to belimited to the disclosed embodiments but, on the contrary, is intendedto cover various modifications and equivalent arrangements includedwithin the scope of the appended claims, which scope is to be accordedthe broadest interpretation so as to encompass all such modificationsand equivalent structures as is permitted under the law.

What is claimed is:
 1. A system comprising: an image sensor configuredto capture an image; one or more motion sensors configured to detectmotion of the image sensor; a mechanical stabilization system, includinggimbals and motors, configured to control an orientation of the imagesensor; an electronic image stabilization module configured to correctimages for rotations of the image sensor; and a processing apparatusthat is configured to: determine a sequence of orientation estimatesbased on sensor data from the one or more motion sensors; based on thesequence of orientation estimates, invoke the mechanical stabilizationsystem to reject motions occurring within a first operating bandwidthwith an upper cutoff frequency; receive the image from the image sensor;based on the sequence of orientation estimates, invoke the electronicimage stabilization module to correct the image for rotations of theimage sensor occurring within a second operating bandwidth with a lowercutoff frequency to obtain a stabilized image, wherein the lower cutofffrequency is greater than the upper cutoff frequency, wherein the firstoperating bandwidth and the second operating bandwidth are substantiallynon-overlapping; and store, display, or transmit an output image basedon the stabilized image.
 2. The system of claim 1, comprising a dronethat is coupled to a housing of the image sensor by the gimbals of themechanical stabilization system.
 3. The system of claim 1, in which theprocessing apparatus is configured to: apply a first filter with a passband matching the first operating bandwidth to the sequence oforientation estimates to obtain data that is input to the mechanicalstabilization system; and apply a second filter with a pass bandmatching the second operating bandwidth to the sequence of orientationestimates to obtain data that is input to the electronic imagestabilization module.
 4. The system of claim 1, in which the processingapparatus is configured to: adjust the first operating bandwidth and thesecond operating bandwidth in a complimentary manner by adjusting theupper cutoff frequency and the lower cutoff frequency by a same amount.5. The system of claim 4, in which the processing apparatus isconfigured to: determine a temperature of the motors of the mechanicalstabilization system; and wherein the upper cutoff frequency and thelower cutoff frequency are adjusted based on the temperature.
 6. Thesystem of claim 5, in which determining the temperature comprises:receiving measurements of current drawn by the motors of the mechanicalstabilization system; and estimating the temperature based on themeasurements of current.
 7. The system of claim 5, in which the uppercutoff frequency and the lower cutoff frequency are adjusted based on adifference between the temperature and a maximum rated temperature forthe motors of the mechanical stabilization system.
 8. The system ofclaim 4, comprising a user interface, and in which the processingapparatus is configured to: receive a mode selection input from the userinterface; and wherein the upper cutoff frequency and the lower cutofffrequency are adjusted based on the mode selection input.
 9. The systemof claim 4, comprising a battery, and in which the processing apparatusis configured to: determine a state of charge of the battery; andwherein the upper cutoff frequency and the lower cutoff frequency areadjusted based on the state of charge.
 10. The system of claim 4, inwhich the processing apparatus is configured to: detect a conditionselected from the group consisting of low light, high motion, highnoise, and high contrast; and wherein the upper cutoff frequency and thelower cutoff frequency are adjusted based on the condition.
 11. Thesystem of claim 1, in which the mechanical stabilization systemcomprises a proportional integral derivative controller withcoefficients tuned to enforce the first operating bandwidth.
 12. Thesystem of claim 1, in which the electronic image stabilization module isimplemented by software executed by the processing apparatus.
 13. Amethod comprising: determining a sequence of orientation estimates basedon sensor data from one or more motion sensors; based on the sequence oforientation estimates, invoking a mechanical stabilization system toreject motions of an image sensor occurring within a first operatingbandwidth with an upper cutoff frequency; receiving an image from theimage sensor; based on the sequence of orientation estimates, invokingan electronic image stabilization module to correct the image forrotations of the image sensor occurring within a second operatingbandwidth with a lower cutoff frequency to obtain a stabilized image,wherein the lower cutoff frequency is greater than the upper cutofffrequency, wherein the first operating bandwidth and the secondoperating bandwidth are substantially non-overlapping; and storing,displaying, or transmitting an output image based on the stabilizedimage.
 14. The method of claim 13, comprising: adjusting the firstoperating bandwidth and the second operating bandwidth in acomplimentary manner by adjusting the upper cutoff frequency and thelower cutoff frequency by a same amount.
 15. The method of claim 14,comprising: determining a temperature of motors of the mechanicalstabilization system; and wherein the upper cutoff frequency and thelower cutoff frequency are adjusted based on the temperature.
 16. Themethod of claim 14, comprising: determining a state of charge of abattery; and wherein the upper cutoff frequency and the lower cutofffrequency are adjusted based on the state of charge.
 17. The method ofclaim 13, in which the mechanical stabilization system includes gimbalsand motors controlled by proportional integral derivative controllers.18. A system comprising: an image sensor configured to capture an image;a mechanical stabilization system, including motors, configured tocontrol an orientation of the image sensor to reject motions occurringwithin a first operating bandwidth with an upper cutoff frequency; andan electronic image stabilization module configured to correct imagesfor rotations of the image sensor occurring within a second operatingbandwidth with a lower cutoff frequency to obtain a stabilized image,wherein the lower cutoff frequency is greater than the upper cutofffrequency, wherein the first operating bandwidth and the secondoperating bandwidth are substantially non-overlapping.
 19. The system ofclaim 18, comprising a drone that is coupled to a housing of the imagesensor by the mechanical stabilization system.
 20. The system of claim18, comprising: a motion tracking module including one or more motionsensors configured to detect motion of the image sensor and determine asequence of orientation estimates for the image sensor; a first filtermodule configured to apply a first filter with a pass band matching thefirst operating bandwidth to the sequence of orientation estimates toobtain data that is input to mechanical stabilization system; and asecond filter module configured to apply a second filter with a passband matching the second operating bandwidth to the sequence oforientation estimates to obtain data that is input to electronic imagestabilization module.